1. Field of the Invention
The present invention relates to injection molding machines. More specifically, the present invention is directed to a method and apparatus for accommodating different size injection die inserts in an injection molding machine.
2. Description of the Prior Art
Injection molding machines using a pair of die frames for carrying respective halves of a pair of injection molding die inserts which are clamped together along a confronting face parting line to form an internal injection molding cavity in the die inserts with means for supplying a plastic material to the cavity to form a desired injection molded product are well-known in the art. An example of such an injection molding machine is manufactured by Polymer Machinery Corporation of Berlin, Conn. and is identified as an Arburg "allrounder" injection molding machine. Die inserts and die frames for such an injection molding machine are manufactured for a particular model of an injection molding machine and are used in matched pairs. An example of such die holders or frames and die inserts are those made by the Master Unit Die Products of Greenville, Michigan and identified as "MUD" frames and unit die inserts. These frames and inserts are designed to be used in matching pairs wherein the large frames are each arranged to accommodate in a recess of the frame a corresponding die insert. The confronting faces of the frames and the die inserts determine the parting line of the molded product. In order to maintain dimensional stability, the frames are of a heavy construction, generally steel, and, in order to change from one size die insert to another die insert, the frame for the first die insert is removed from the machine and replaced with a frame for the second die insert. Inasmuch as this prior art operation involves a substantial rearrangement of the molding machine and involves the handling of a heavy frame, the operator time and down-time for the injection molding machine are a substantial part of the molding process. Since such a changeover may occur daily or even more than once a day, the changeover time is a significant part of the cost of producing the molded product. Further, such prior art frames and die inserts have no provision for accommodating a die insert which extends past the confronting faces of the frames inasmuch as the frames and die inserts are arranged to have coplaner faces to determine the parting line and to distribute the compression forces therebetween. Accordingly, in order to eliminate these problems associated with the prior art injection molding apparatus, it is desirable to provide frames and die inserts which are interchangeable while also accommodating non-coplaner die inserts and frames.